I was having some strange IE blowups that seemed to occur after I Installed Silverlight 2.0. I decided to uninstall Silverlight and see if the issue was occurring because of it. After fiddling around a bit I discovered that the issue was occurring because of Flash.
So being still very excited to get into Silverlight I proceeded to re-install the SDK. I was promptly welcomed to ‘You cannot install because ..” message. Well I was able to install earlier and the only thing that changed was I had installed Silverlight before. Well I decided to to a no-no and go into the registry and folder structure and remove any reference to Silverlight, there were many. Long story short, after deleting all registry keys and a couple of folders I was able to install Silverlight again.
Be wary, uninstall does not actually uninstall.